bq20z45

The FETs will turn on when the Impedance Track enable command is sent (0x0021 to Manufacturer Access).  The FETs could be off if there were a 1st or 2nd Level Safety condition or if the system present pin is not grounded if NR=0 in Operation Cfg B.  For "test purposes" (before enabling Impedance Track), there is a command that can control the FETs.  By sending 0x0006 to command 0x46 both FETs will turn on.  Otherwise, both FETs will be off.  This is so safety testing can be done before the gauging algorithm is enabled.

Thanks for the response.

So what I did was I sent the 0x0021 command to Manufacturer Access to turn the FETs on and I sealed the chip like that. Now I see that when I unplug the batteries and replug them in, the CHG and DSG bits in the FET Control Register stay on. However, when I disconnect and reconnect the batteries like this, I notice that I do not read the battery's voltage accross Pack + and Pack - until I apply a voltage of 5.5V - 25V momentarily to Pack + (as instructed in Section 8 of the EVM User's Guide to awaken the chip). Could you please explain why this is required?

Thanks!

The circuitry is set up so that the battery drives the BAT pin of the AFE.  However, a voltage needs to be momentarily applied to the PACK pin to power up the AFE.  After that, the battery takes over with providing power.

Okay, I see that Pack pin (pin 2) is what senses the voltage to come out of shut down mode. I guess my question now is, is there any way to remove the batteries and replace them and have the FETs already be on without having to apply a voltage? The design that I am implementing this system into is powered by the batteries, so I wouldn't have another voltage source to apply to this pin and I don't want to bypass the FETs with a switch or something due to safety reasons. I see that there is a Battery Removed Mode for the chip, but it does not seem to solve the problem. Any ideas? Your help is greatly appreciated.

The voltage you would normally apply to the PACK pin comes from the charger.  The gauge will stay on indefinitely, unless the cells are discharged to the point of entering shutdown mode.  If that occurs the charger will need to connected again to bring it out of shutdown mode and to charge the battery.

The battery removed mode is there for batteries that can be removed from the system (such as in a notebook computer).  The FETs will turn off, eliminating the chance for a short circuit between the PACK+ and PACK- terminals of the connector.  Once reinserted, the System Present pin will detect this and turn the FETs back on.  So this function is unrelated to what you want to do.

So, in short, no.  There is not a way to removed the cells and reconnect new ones without applying a charger voltage to power up the device afterwards.

Thank you very much for your help Chase. This chip really is great and is a very powerful tool. The only trouble I am having with it is its documentation unfortunately. Which leads me to my next question...

I saw that there is an AutoCycle feature, but can't find any mention of it at all in any of the documents I have been looking through. I tried testing it out by setting a percentage that I wanted it to stop discharging at and gave it a relaxation time to wait before charging. I clicked on Start AutoCycle and began discharging the battery, but nothing happened when it got to the percentage that I set. Are there other things that must be done to set up this feature? Thanks in advance!

Jon, in the EVSW pulldown menu for AutoCycle there should be a menu option called 'AutoCycle Options...'.  Click on this, and in the top right is a menu button called 'Hardware Setup Help...'.  This will guide you through setting up the hardware and point you to the pins on the EV2300 used for control.  I believe a simple relay or FET circuit will need to be assembled.